Morphological and phylogenetic characterization of Fusarium Link

Identification of Fusarium isolates in a sample at the species level is an important and difficult task because many Fusarium species have similar morphological characteristics. The phylogenetic relations of species have been applied in Fusarium systematic and may solve taxonomic difficulties. The aim of the present study is to characterize pathogeny of Fusarium isolates through morphological analysis (concept of morphological species) associated with symptoms in hosts together with phylogeny analysis (concept of phylogenetic species) using internal transcribed spacer region (ITS) of ribosomal DNA for species identification. For the morphological characterization, Fusarium isolates were grown in PDA culture medium. Then, they were classified based on colony color and the microconidial, macroconidial and chlamydospore structures. The isolates were characterized molecularly by amplifying and sequencing the ITS region of the ribosomal DNA. The sequences generated were compared with those placed in the Genbank and Maximum Likelihood phylogenetic trees were constructed. Out of 14 isolates characterized morphologically and molecularly, five isolates were grouped in the Gibberella fujikuroi species complex in the Liseola section, seven presented characteristics of species from the Elegans section within the F. oxysporum species complex and two isolates presented characteristics of the section Gibbosum species complex in the F. incarnatum-equiseti species complex. Thus, seven isolates (section Elegans) belonged to the species F. oxysporum, two isolates (section Gibbosum) to the species F. equiseti. However, the ITS region of the ribosomal DNA did not provide sufficient evidence to define the species of G. fujikuroi species